Monitoring Groundwater Levels in Sierra Leone

Thursday, 4 August 2016 09:05:00 Europe/London

Equipment survives in challenging field conditions

Since November 2012 I have been working on a UK Aid project funded by the UK Department for International Development (DFID) in which my role has been to assist, with others, the Ministry of Water Resources to develop a pilot groundwater monitoring network in The Rokel-Seli River Basin.

Part of my work has involved installing groundwater level loggers and other monitoring equipment in wells and boreholes and in providing training, practical support and mentoring to a group of young professionals from the Ministry of Water and other organisations. They in turn have been expected to take on the responsibility for managing these networks and for the collection of data by building and sustaining working partnerships with local communities and District Councils. For more information on the project, including maps, and data produced during the course of the project, go to http://www.salonewatersecurity.com/

Groundwater level data was collected by loggers at 15 minute intervals. Data was downloaded every 2 to 4 months. Manual water levels were taken when visiting sites to validate the logger records. This provided a high degree of confidence in the data record (Figure 2). These data were also matched against rainfall records which were taken daily at community rainfall stations set up by the project.

We learnt:

Rainfall totals on average exceed 3000 mm / year, which is over 3 times the average for England and Wales. Nearly all of this rain falls within a 7 month period extending from May to November. Rainfall at the height of the wet season can exceed 100 mm per day. Figure 2 Groundwater level and rainfall records, 2013 to 2016.

Across the 16 wells and boreholes monitored for this project, annual groundwater levels varied from 2.5 to over 10 metres, with the average being around 5.5 metres. Many wells are dry, or severely stressed towards the end of the dry season.

Groundwater levels rise within a few days of the start of the wet season, typically reaching a peak by mid-August (Figure 2) and receding thereafter. By mid-March groundwater is virtually fully discharged.

The fact that equipment has survived and is still in use and providing high quality data 3 years after deployment is a real testimony to the reliability of the In-Situ equipment.

Ebola - Equipment Donation

It is worth mentioning that during the Ebola crisis of 2014-2015, In-Situ donated 11 Water Level Dip Tapes to the Sierra Leone Ministry of Water Resources.

At that time Sierra Leone was in the grip of the worst Ebola outbreak in history and the dip tapes were used to monitor groundwater levels at wells and boreholes adjacent to Ebola Care Facilities. Since then the tapes will have been distributed to District Councils to help towards establishing a national groundwater-monitoring network.